The present subject matter relates generally to a drilling rig, and more particularly to a multipurpose cantilever skidding frame that can be employed in a drilling rig. The present subject matter also relates to a drilling rig having a multi-direction direct cantilever skidding system that can be employed in a Jackup drilling unit or other types of mobile platforms.
The wells to be drilled may be arranged in a grid, requiring the drilling derrick to be moved in both longitudinal and transverse directions to access the various locations of the wells. In a traditional cantilever arrangement, a Jackup drilling unit or other mobile platform may access wells through a combination of a longitudinal motion of the cantilever that skids in and out of the Jackup hull, and a transverse skidding of the drill floor at the end of the cantilever. This arrangement may be effective if the well pattern is contained within a small envelope; however, the extent to which the drill floor can skid in a transverse direction is limited. In addition, as the load is significantly offset from the cantilever center to access the side wells loads on the side of the cantilever in the direction of the offset will be increased, usually resulting in a reduced load capacity for extreme transverse drilling positions.
A cantilever skidding system allowing a cantilever to skid in both longitudinal and transverse directions is disclosed in U.S. Pat. No. 6,171,027. In this system, a drill floor is fixedly mounted to a cantilever to solve the offset problem caused by the movable Jackup drilling unit. The transverse reach of the drill floor is enabled by the transverse cantilever skidding. The cantilever is movably connected to the supporting members which are movably connected to transverse rails. The cantilever moves longitudinally over the supporting members, and the cantilever together with the supporting members move transversely over the transverse rails. The supporting members thus support the cantilever at all times and carry the full weight of the cantilever even when it is retracted. During installation, the supporting members must be accurately aligned, and then the heavy cantilever, must be lifted and slowly slid into the supporting members. Such an operation is both challenging and complex. Further, once installed the supporting members are always under load and are therefore not able to be easily accessed for inspection and maintenance.